In capillary electrophoresis methods, ions that have gathered on the inner wall of a capillary tube migrate upon voltage application to generate an electroosmotic flow, which causes migration of a sample; thus, electrophoresis is carried out. Furthermore, hemoglobin (Hb) in blood reacts with glucose in the blood to become glycated Hb. The glycated Hb in the blood reflects the past history of the blood glucose level in a biological body and, therefore, is considered as an indicator in, for example, the diagnosis and treatment of diabetes. Among such glycated Hb, hemoglobin A1c (HbA1c) is measured by laboratory tests and the like as an especially important indicator. HbA1c is glycated at the beta chain N-terminal valines. Also, hemoglobin S (HbS) is a molecule that causes sickle cell anemia, and so is important in diagnosis. In HbS, the 6th glutamic acid (Glu) in the beta chains is substituted with valine (Val). Accordingly, there is a demand for a technique for precisely analyzing various hemoglobins, such as HbA1c and HbS. Examples of methods for measuring hemoglobin in blood include agarose electrophoresis methods, capillary electrophoresis methods, HPLC methods, immunological methods, enzymatic methods, and the like. Among these, those allowing minute variations such as genetic variants of hemoglobin to be detected are capillary electrophoresis methods and HPLC methods. Furthermore, an apparatus for analyzing hemoglobin is required to be relatively small in size. With respect to this point, it is difficult to reduce the size of the whole apparatus in HPLC methods. On the other hand, capillary electrophoresis methods allow the size of the whole apparatus to be reduced, with the apparatus being formed into a microchip.
However, the precision of the analyses of various hemoglobins is insufficient in conventional capillary electrophoresis methods. With respect to this point, as a technique for precisely analyzing HbA1c, there is a technique in which the inner wall of a capillary tube is coated with a protein, which is then coated with a polysaccharide (Patent Document 1) (hereinafter, referred to as a “conventional technology (1)”). However, conventional technology (1) is problematic in that normal hemoglobin (HbA0) and HbS cannot be separated, and their peaks overlap. The fact that HbA0 and HbS cannot be separated means that the ratio of HbA1c in blood cannot be measured accurately. That is to say, conventional technology (1) is problematic in that the measured HbA1c of a patient suffering from sickle cell anemia is artificially low. As a method for solving this problem, there is a method in which capillary electrophoresis is carried out with a zwitterionic type of running buffer that is allowed to contain a flow inhibitor such as aliphatic diamine, where the inner wall of the capillary tube is not coated (Patent Document 2) (hereinafter, referred to as a “conventional technology (2)”). However, the conventional technology (2) needs a long period of time (e.g., 10 minutes) for measurement. Accordingly, conventional technology (2) cannot be applied substantially to laboratory tests in which many samples are required to be processed in a short period of time. Furthermore, in conventional technology (2), a long capillary tube is required. Thus, when using conventional technology (2), the apparatus cannot be made smaller. Moreover, in conventional technology (2), HbA1c cannot be measured although HbA0 and HbS can be separated.
[Patent Document 1] JP 9(1997)-105739 A
[Patent Document 2] JP 2006-145537 A